1. Field of the Invention
The present invention relates to a photoresist composition for digital exposure and a method of fabricating a thin film transistor (TFT) substrate using the photoresist composition.
2. Discussion of the Background
Liquid crystal displays (LCDs) are some of the most widely used flat panel displays. The LCD includes two substrates on which field-generating electrodes are formed, and a liquid crystal layer that is interposed between the substrates. In the LCD, a voltage is applied to the electrodes to rearrange the liquid crystal molecules of the LCD, thereby controlling the quantity of transmitted light.
An LCD includes micro-circuit patterns, which are generally formed by photolithography. A photoresist and a mask are used during the photolithography process for forming a micro-circuit pattern. During the photolithography process, light is irradiated into a mask having a micro-circuit pattern shape. Only the light passing through the mask is irradiated into the photoresist, and a photoresist pattern is formed by the light irradiated into the photoresist. The photoresist is then subjected to an etching process, thereby forming the micro-circuit pattern. According to a recent trend for large-screen sized LCDs, masks used in the manufacture of the LCDs are becoming large-sized, which increases the mask fabrication cost, thereby increasing the LCD's manufacturing cost. Accordingly, a method of manufacturing an LCD by maskless photolithography using a digital exposure apparatus has recently been proposed.
However, a laser beam, i.e., a light source used during digital exposure, has an energy density that is close to a Gaussian distribution. Thus, the quality of light is constant at a laser beam overlapping area, while the quality of light is not constant around the laser beam overlapping area. Accordingly, when photoresist patterns are formed through digital exposure, the photoresist patterns positioned at peripheral areas of laser beam irradiation spots may not provide a taper angle and a pattern profile that are satisfactory for an etching process. Therefore, an object of the present invention is to develop a photoresist composition that may overcome the disadvantages associated with digital exposure.